A young Lois Lane and her sister Lucy play with chimpanzee named Titano. Lois's father arrives and takes Titano to the space center where he is placed onboard a rocket and shot into space. As Lois watches from the space center the rocket veers off course and Titano is lost.
Twenty Years later, a space-suited Superman flies in space and stops a meteor storm from colliding with a space station. After investigating one of the meteors, Superman discovers a space capsule that contains a still-breathing, but unconscious Titano.
Later, in Star Labs Clark Kent talks with Professor Hamilton about Titano. Professor Hamilton is mystified as to how Titano could have survived and why he's twice as heavy as when he was shot into space. Lois arrives and happy greats Titano. Seeing how lively Titano has become, Professor Hamilton suggests that Lois take Titano home with her.
Lois takes Titano home. Unfortunately, he begins to make a mess. As she lays down to take a rest, she does not notice Titano begin to glow and grow. Later, Jimmy comes to Lois's apartment to take some pictures of the Lois and Titano. Lois manages to talk Jimmy into babysitting for Titano and leaves.
While Jimmy watches Titano, he is stunned to see him grows to the size of a person. Meanwhile at Starr Labs, Superman confers with Professor Hamilton about the strange properties of gas pockets in the meteor in which Titano was found.
Suddenly from the lab, Superman hears a scream. In the lab, three technicians are being attacked by enormous bacteria like creatures. Superman and Professor Hamilton manage to stop the creatures. Professor Hamilton informs Superman that the creatures were bacteria exposed to the gas from the meteor. They realize that the same thing may happen to Titano.
At Lois's apartment, Jimmy calls Lois and asks her to come black. Titano is destroying her apartment. Suddenly Titano again doubles in size. Jimmy runs to Lois's porch. There he slips on a banana peel and falls from the building.
Superman arrives just in time to catch Jimmy. Superman heads to Lois's apartment, but when they arrive, Titano is gone. Lois arrives and screams when she sees her apartment in ruins.
At the zoo, an enormous Titano releases a group of caged monkeys. The monkey's release other animals as Titano grows to the size of a building. Superman comes to the zoo and recaptures the escaped animals.
Titano then heads to the dockyard and begins to consume a shipment of bananas. SCU and the police arrive. They try to knock Titano unconscious with darts. They only manage to anger him. Eventually Superman arrives, but is quickly caught by Titano and thrown into a police car.
Titano heads off with Superman is pursuit. Lois also follows. She gets a call from her father who has a small music playing stuffed monkey that Lois and Titano played with when she was a child. At an amusement park, Superman battles Titano. Lois arrives with the doll and after almost losing it she heads for the intercom where she plays the doll's song "Pop Goes the Weasel". Titano calms down long enough for SCU to use knock out gas on him.
Later with Titano's uncontrollable growth stopped, he is shipped off to an island. Lois says goodbye and flies off with Superman. Titano stays on the island with his favorite stuffed animal worn on a chain around his neck.